Abstract: Electronic interfaces to neural devices are fundamentally incompatible with the natural neural system. Due to the vast difference in current densities involved the electrical domain is well suited to record from neural systems but not suited for stimulation. A neural interface that provides simultaneous recording and stimulation without any stimulus artifact would truly transform the way we study, manipulate and interact with neural systems. Neurotrnsmitter based neural interfaces, are most natural but the neurotransmitter must be stored or gener- ated in-situ increasing the risk and difficulty of the interface design. This proposal outlines an electrochemical interface that circumvents these issues by using potassium ions that are sequestered from the extracellular fluid to chemically stimulate neural systems. The required concentration of ions for chemical stimulation is only 2-3X over the background concentration of 5mM. This enables the scaling of this method to the scope of the natural neural architecture which is not currently possible with electrical neural interfaces. Additionally, by building a truly biocompatible interface, some of the key issues of implant longevity can be addressed. This proposal address the challenges of building this unique electrochemical interface by integrating advances in the fields of electrical engineering, materials, chemistry and neuroscience. Potential Impact: The prime societal impact of this work is in the area of neural prosthetic devices. The design of a more efficient neural interface will enable the building of advanced devices that can alleviate some of the de- bilitating conditions that are faced by those suffering from neurological diseases. Apart from the field of medicine the concepts that are advanced by this proposal can be applied to furthering our understanding of neuroscience, organic electronics, membrane separation, understanding the physics of self-assembly and polymer synthesis. Public Health Relevance: The major goal of this project is to develop a biocompatible, high-density neural interface for neural prosthetic devices. The design of a more efficient neural interface will enable the building of advanced devices. These devices can potentially alleviate the suffering faced by patients with debilitating neurological conditions such as retinal degeneration, spinal cord injury and paralysis. Such a device can also help in further our understanding of neuroscience by allowing for simultaneous stimulation and recording from a large population of neurons.